1. Field of the Invention
This invention relates generally to wrapping machines and, more particularly, to wrapping machines for wrapping film material or the like around metal coils such that the film material is deposited on the coil in overlapping layers which extend through a central opening of the coil.
2. Description of the Related Art
While this invention will be described principally with reference to wrapping metal coils with a central opening, it will be appreciated that many other types of annular products with a central opening, such as wire, paper, cable, tires, etc., can also be wrapped according to the invention.
In order to protect the metal coils, it is conventional practice to wrap the coils in a substantially water impermeable, pliable, flexible wrapping medium such as a stretch wrap thermoplastic film, such as polyvinyl chloride or polyethylene, which is chemically inert, provides protection against water and other liquids, vapors and gases, and which tends to cling to itself.
The film is stretched prior to or during application and due to its property of memory, it then seeks to return to its unstretched state. Such film materials are generally applied in either sheet form, wherein the entire article to be wrapped is simply enveloped in the sheet and any side seams may be heat sealed, or in strip form in which a strip of film is wound continuously around the article, which is rotated about an axis perpendicular to the axis of wrap application during wrapping so that eventually the entire peripheral surface of the article is covered. The devices that relate to the strip form of wrapping film typically use a separate film tensioning device for maintaining a suitable film tension. These devices constantly require adjustment by trained mechanics in order to maintain the suitable film tension required for proper wrapping to take place.
There is a need, therefore, for an improved wrapping method and apparatus which will provide complete, hermetic, protection for the wrapped metal coil without the addition of a separate film tensioning device for maintaining a suitable film tension during the wrapping process.
This invention provides a method and apparatus for wrapping a coil having a central axial opening in film material without the use of a separate film tensioning device for maintaining a suitable film tension. The method and apparatus includes the use of a guide arm and article turning gear. The guide arm, in turn, supports a ring member. The ring member is in the form of a split frame having an inside and outside diameter and rotates about a ring axis.
A drive wheel is mounted on the guide arm. The drive wheel is rotatable about a vertical axis and is in frictional engagement with the outside diameter of the ring member. The drive wheel may be driven by a motor with gearing.
A plurality of guide rollers are mounted upon the guide arm and support the ring member. The guide rollers are angularly spaced apart about the ring member axis and rotatable about vertical axes. The guide rollers are disposed adjacent to both the inside and outside diameters of the frame of the ring member.
A film material carriage member containing a film roll is adjustably mounted on the ring member and the film roll is carried by the ring member through the central axial opening and around the external surfaces of the coil.
Means for causing the film carriage member to follow an orbital path are provided. The orbital path introduced to the film material carriage member through these means, eliminates a need for having a separate film tensioning device for taking-up tension on the film material during the wrapping process.
In a first embodiment of the invention, the means for causing the film carriage member to follow an orbital path is in the form of a motorized cam device connected to a guide frame. The guide frame is mounted on linear ball slides that are attached to the guide arm. The guide arm is provided with an oscillating motion, i.e, a left-right motion.
In a second embodiment of the invention, the means for causing the film carriage member to follow an orbital path is in the form of one or more film holding arms that rotate with the ring member. The film carriage means is attached to one end of the film holding arm. The other end of the film holding arm is mounted onto the ring member. The film holding arm is provided with an elliptical motion as it rotates with the ring, member.
In each of the embodiments described above, the orbital path provided for the film carnage member is synchronized to the rotation provided by the article turning gear.
The article turning gear positions and supports the article as it loaded into the guide arm. Once loaded, the article turning gear then rotates the article during the wrapping process.